1. Field of the Invention
The present invention relates to an organic electroluminescence (EL) device, and more particularly, to an organic EL device which is simply manufactured by forming an electron transport layer by a spin-coating method.
2. Description of the Related Art
An EL device as a spontaneous luminescence type display has a broad viewing angle, good contrast and response time characteristics. Due to these merits, the EL device has been the focus of next generation displays.
The EL device is classified into an inorganic EL device and an organic EL device depending on the material used for a light-emitting layer. In particular, the organic EL device has good luminance, driving voltage and response time, and can display a multitude of colors.
FIG. 1 is a section view showing the structure of a general EL device. Referring to FIG. 1, an anode 12 is formed on a substrate 11. A hole transport layer 13, a light-emitting layer 14, an electron transport layer 15, and a cathode 16 are formed on the anode 12 in sequence. Here, the hole transport layer 13, the light-emitting layer 14 and the electron transport layer 15 are organic thin films made of an organic compound.
The organic EL device having the above structure operates based on the following operation principle. When a voltage is applied between the anode 12 and the cathode 16, holes injected from the anode 12 move through the hole transport layer 13 to the light-emitting layer 14. Meanwhile, electrons are injected from the cathode 16 through the electron transport layer 15 to the light-emitting layer 14. Also, carriers are recoupled in the light-emitting layer 14 to generate excitons. The excitons are transited from an excited state to a ground state, so that fluorescent molecules of the light-emitting layer emit light to form a picture.
Also, in general, the electron transport layer is formed of quinolinol complex, benzoquinolinol complex, 1,3,4-oxadiazole derivative, triazole derivative or phenanthroline derivative.
However, when the electron transport layer is formed of the compounds, using a spin coating method is not possible. That is, only a vapor-deposition method should be used. This is because the light-emitting layer is damaged by the solvent used for spin-coating the compounds.
To solve the above problems, it is an object of the present invention to provide an organic electro-luminescence (EL) device which is simply manufactured by forming an electron transport layer by a spin-coating method.
To achieve the above object, there is provided an organic electroluminescence (EL) device comprising an electron transport layer formed between a pair of electrodes, wherein the electron transport layer comprises 50xcx9c99.9 wt % of alcohol-soluble polymer and 0.1xcx9c50 wt % of electron transporting material.